1. Field of the Invention
The present invention relates to a catalyst for polymerization and co-polymerization of ethylene, or more particularly to a solid titanium catalyst supported onto a carrier containing magnesium, which has a very high catalytic activity with excellent catalyst morphology.
2. Description of the Relevant Art
Catalysts containing magnesium for polymerization and co-polymerization of ethylene are known to have very high catalytic activities and to accord high bulk density, which are suitable for liquid or gas phase polymerization. By liquid phase polymerization of ethylene, it denotes a polymerization process performed in a medium such as bulk ethylene, isopentane, or hexane, and as for the important characteristics of the catalyst used in this process, they are as follows: high activity, bulk density of produced polymers, the amount of low molecular weight polymer dissolved in a medium, etc. Of these characteristics, it could be said that catalytic activity is the most important characteristics of a catalyst.
Many of the titanium-based catalysts containing magnesium for olefin polymerization, and the manufacturing methods thereof have been reported. Especially, many processes making use of magnesium solutions to obtain olefin polymerization catalysts of high bulk density have been known. There is a means of obtaining magnesium solution by reacting a magnesium compound with an electron donor such as alcohol, amine, cyclic ether, or organic carboxylic acid in the presence of a hydrocarbon solvent. As for the cases of using alcohol, they are disclosed in U.S. Pat. Nos. 4,330,649 and 5,106,807. Further, a method for producing a magnesium-supported catalyst by reacting a liquid-phase magnesium solution with a halogen compound such as titanium tetrachloride is well known. Although these types of catalysts provide high bulk density, there are disadvantages at the production stage, such as a need for improvement with respect to catalytic activity, a large quantity of expensive TiCl4 in use, and a large amount of hydrogen chloride produced during the manufacturing process.
U.S. Pat. No. 5,459,116 discloses a method of producing a solid titanium catalyst by contact-reacting a magnesium solution having an ester of at least one hydroxy group as an electron donor with a titanium compound. By using this method, a catalyst with a high polymerization activity and superior bulk density of polymers may be obtained. Yet, there are disadvantages at the production stage, such as a large quantity of expensive TiCl4 in use, and a large amount of hydrogen chloride produced during the manufacturing process.
U.S. Pat. No. 4,843,049 discloses a method of producing a catalyst having high titanium content by reacting a magnesium chloride-ethanol substrate, produced by spray-drying, with titanium alkoxide, followed by reacting diethyl aluminum chloride or ethyl aluminum sesquichloride. However, this method has disadvantages of having alcohol content outside the range of 18-25% and deteriorating bulk density of polymers produced when compounds other than diethyl aluminum chloride or ethyl aluminum sesquichloride are used. Further, there is a problem of setting the titanium content to at least 8 wt % or more in order to obtain high catalytic activity.
U.S. Pat. Nos. 5,726,261 and 5,585,317 disclose a method of producing a catalyst having a porosity of 0.35xcx9c0.7, supported with a titanium compound having at least one titanium-halogen and one hydroxy group, by treating the magnesium-ethanol substrate produced by means of a spray-drying method with triethyl aluminum, or heat-treating the same, and then treating it with a titanium alkoxide compound, titanium alkoxide or silicon tetraethoxide, etc. Yet, this method has a disadvantage of somewhat low catalytic activity.
As shown above, there is a need for the development of a new catalyst for polymerization or co-polymerization of ethylene with the following conditions: simple manufacturing process, high polymerization activity while not using a large amount of expensive titanium compounds, and high bulk density of polymers by means of controlling the catalyst particles. In an embodiment recited herein is disclosed a method for producing, from low-cost compounds via a simple process, a catalyst having excellent catalytic activity, capable of producing polymers of high bulk density by controlling the catalyst particle morphology.
Consequently, one embodiment described herein is directed to a new catalyst for polymerization or co-polymerization of ethylene, wherein said catalyst has enhanced catalytic activity and is capable of producing polymers of high bulk density.
An advantage of the disclosed method is to provide a simple process specifically for producing a catalyst for polymerization or co-polymerization of ethylene.
A solid titanium catalyst of high catalytic activity, capable of producing polymers having high bulk density as described herein, is produced by a simple yet efficient manufacturing process, which includes (i) preparing a magnesium solution by contact-reacting a halogenated magnesium compound with alcohol; (ii) reacting the same with an ester compound that includes at least one hydroxy group, or a silicon compound containing an alkoxyl group and a phosphorous compound; (iii) reacting the same with an aluminum compound, and then producing a solid titanium catalyst by adding a titanium compound, or a titanium compound and a vanadium compound.
Examples of halogenated magnesium compounds used in the present invention are as follows: di-halogenated magnesium such as magnesium chloride, magnesium iodide, magnesium fluoride, and magnesium bromide; alkymagnesium halides such as methylmagnesium halide, ethylmagnesium halide, propylmagnesium halide, butylmagnesium halide, isobutylmagnesium halide, hexylmagnesium halide, and amylmagnesium halide; alkoxymagnesium halides such as methoxymagnesium halide, ethoxymagensium halide, isopropoxymagnesium halide, butoxymagnesium halide, octoxymagnesium halide; and aryloxymagnesium halides such as phenoxymagnesium halide and methyl-phenoxymagnesium halide. Of the above magnesium compounds, two or more compounds may be used in a mixture. Further, the above magnesium compounds may be effectively used in the form of a complex compound with other metals.
Of the compounds listed above, some may be represented by a simple chemical formula, but the others cannot be so represented depending on the production methods of magnesium compounds. In the latter cases, it may be generally regarded as a mixture of some of the above listed compounds as follows: compounds obtained by reacting a magnesium compound with a polysiloxane compound, a silane compound containing halogen, ester, alcohol, etc.; and compounds obtained by reacting a magnesium metal with alcohol, phenol, or ether in the presence of halosilane, phosphorus pentachloride, or thionyl chloride. However, the preferable magnesium compounds are magnesium halides, especially magnesium chlorides or alkylmagnesium chlorides, preferably those having an alkyl group of 1xcx9c10 carbons; alkoxymagnesium chlorides, preferably those having an alkoxy group of 1xcx9c10 carbons; and aryloxymagnesium chlorides, preferably those having an aryloxy group of 6xcx9c20 carbons. The magnesium solution used may be made by dissolving the aforementioned compounds in alcohol solvent in the presence or absence of a hydrocarbon solvent.
Examples of the types of hydrocarbon solvents used in the present invention are as follows: aliphatic hydrocarbons such as pentane, hexane, heptane, octane, decane, and kerosene; alicyclic hydrocarbons such as cyclobenzene, methylcyclobenzene, cyclohexane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, cumene, and cymene; and halogenated hydrocarbons such as dichloropropane, dichloroethylene, trichloroethylene, carbon tetrachloride, and chlorobenzene.
When a magnesium compound is converted into a magnesium solution, alcohol is used in the presence or absence of the aforementioned hydrocarbons. The types of alcohol include those containing 1xcx9c20 carbon atoms, such as methanol, ethanol, propanol, butanol, pentanol, hexanol, octanol, decanol, dodecanol, octadecyl alcohol, benzyl alcohol, phenylethyl alcohol, isopropyl benzyl alcohol, and cumyl-alcohol, or preferably an alcohol containing 1xcx9c12 carbon atoms. The average size of a target catalyst and its particle distribution can vary according to the following factors: types of alcohol, the total contents, types of magnesium compounds, the ratio of magnesium to alcohol, etc. Nevertheless, the total amount of alcohol required to obtain magnesium solution is at least 0.5 mol per each mole of a magnesium compound, preferably about 1.0xcx9c20 mol, or more preferably about 2.0xcx9c10 mol.
The reaction of a magnesium compound with alcohol for producing a magnesium solution is preferably carried out in the presence of a hydrocarbon medium. While it varies depending on the types and the amounts of alcohol and aromatic ether, the reaction temperature should be at least xe2x88x9225xc2x0 C., preferably xe2x88x9210xcx9c200xc2x0 C., or more preferably about 0xcx9c150xc2x0 C. It is preferable to carry out the reaction for about 15 minutesxcx9c5 hours, preferably for about 30 minutesxcx9c4 hours.
Of the electron donors used in the present invention, the ester compounds containing at least one hydroxy group include unsaturated aliphatic acid esters having at least one hydroxy group such as 2-hydroxy ethylacrylate, 2-hydroxy ethylmethacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropylmethacrylate, 4-hydroxybutylacrylate, pentaerithritol triacrylate; aliphatic monoesters or polyesters containing at least one hydroxy group such as 2-hydroxy ethyl acetate, methyl 3-hydroxy butylate, ethyl 3-hydroxy butylate, methyl 2-hydroxy isobutylate, ethyl 2-hydroxy isobutylate, methyl-3-hydroxy-2-methyl propionate, 2,2-dimethyl-3-hydroxy propionate, ethyl-6-hydroxy hexanoate, t-butyl-2-hydroxy isobutylate, diethyl-3-hydroxy glutarate, ethyl lactate, isopropyl lactate, butyl isobutyl lactate, isobutyl lactate, ethyl mandelate, dimethyl ethyl tartrate, ethyl tartrate, dibutyl tartrate, diethyl citrate, triethyl citrate, ethyl-2-hydroxy-caproate, diethyl bis-(hydroxy methyl) malonate; aromatic esters having at least one hydroxy group such as 2-hydroxy ethyl benzoate, 2-hydroxy ethylsalicylate, methyl-4-(hydroxy methyl) benzoate, methyl-4-hydroxy benzoate, ethyl-3-hydroxy benzoate, 4-methyl salicylate, ethyl salicylate, phenyl salicylate, propyl-4-hydroxy benzoate, phenyl-3-hydroxy naphthanoate, monoethylene glycol monobenzoate, diethylene glycol monobenzoate, triethylene glycol benzoate; alicyclic esters having at least one hydroxy group such as hydroxy butyl lactone. The amount of an ester compound containing at least one hydroxy group should be 0.001xcx9c5 mol per mole of magnesium compound, or preferably 0.01xcx9c2 mol per mole.
Another electron donor compound used in the present invention is expressed by the following general formula: PXaR1b(OR2)c or POXdR3e(OR4)f. Here, X is a halogen atom, and R1, R2, R3, or R4 is a hydrocarbon of an alkyl, alkenyl or aryl group, having 1xcx9c20 carbon atoms. Moreover, the following conditions are provided: a+b+c=3, 0xe2x89xa6axe2x89xa63, 0xe2x89xa6bxe2x89xa63, 0xe2x89xa6cxe2x89xa63, d+e+f=3, 0xe2x89xa6dxe2x89xa63, 0xe2x89xa6exe2x89xa63, and 0xe2x89xa6fxe2x89xa63.
More specifically, for example, it includes phosphorus trichloride, phosphorus tribromide, diethylchlorophosphite, diphenylchlorophosphite, diethylbromophosphite, diphenylbromophosphite, dimethylchlorophosphite, phenylchlorophosphite, trimethylphosphite, triethylphosphite, tri-n-butylphosphite, trioctylphosphite, tridecylphosphite, triphenylphosphite, triethylphosphite, tri-n-butylphosphate, and triphenylphosphate. Other phosphor compounds satisfying the aforementioned formula may be used. As for the amount used, 0.25 mole or below per 1 mole of magnesium compound is appropriate, or more preferably 0.2 mole or below per 1 mole.
As for the silicon compound having an alkoxy group, another electron donor, it is preferable to use a compound having a general formula of RnSi(OR)4xe2x88x92n (R is a hydrocarbon having 1-12 carbon atoms, and n is a natural number of 1xcx9c3). More specifically, the following compounds, for example, can be used: dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, methylphenylmethoxysilane, diphenylethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, vinyltriethoxysilane, butyltriethoxysilane, phenyltriethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane, ethylsilicate, butylsilicate, and methyltriaryloxylsilane. As for the amount used, 0.05xcx9c3 moles per 1 mole of magnesium compound is preferable, or more preferably 0.1xcx9c2 moles.
As for the temperature used during contact-reaction of a liquid magnesium compound solution with an ester compound having at least one hydroxy group, or a phosphorous compound and silicon solution having an alkoxy group, the temperature of 0xcx9c100xc2x0 C. is appropriate, or more preferably 10xcx9c70xc2x0 C.
The magnesium compound solution reacted with said electron donors causes re-crystallization of catalyst particles by reacting with a mixture of a liquid titanium compound of general formula of Ti(OR)aX4xe2x88x92a(R for a hydrocarbon group, X for a halogen atom, and xe2x80x9caxe2x80x9d for a natural number of 0xe2x89xa6axe2x89xa64) and a silicon compound of a general formula of RnSiCln-4 (R for hydrogen, an alkyl group of 1xcx9c10 carbons, an alkoxy, haloalkyl, aryl, halosilylalkyl group, or a halosilyl group of 1-8 carbon atoms, and n for a natural number of 0xe2x89xa6axe2x89xa63).
Examples of titanium compounds which satisfy the general formula of Ti(OR)aX4-a include 4-halogenated titanium such as TiCl4, TiBr4, and TiI4; 3-halogenated alkoxy-titanium such as Ti(OCH3)Cl3, Ti(OC2H5)Cl3, Ti(OC2)3, Ti(O(I-C4H9))Br3, and Ti(O(i-C 4H9)Br2; 2-halogenated alkoxy-titanium such as Ti(OCH3)2Cl2, Ti(OC2H5)2Cl2, Ti(O(i-C4H9)2Cl2, and Ti(OC2H5)2Br2; and tetra-alkoxy titanium such as Ti(OCH3)4, Ti(OC2H5)4, and Ti(OC4H9)4. A mixture of the above titanium compounds can also be used in the present invention. However, the preferable titanium compounds are those containing halogen, or more preferably titanium tetrachloride.
Examples of silicon compounds satisfying the above general formula of RnSiCl4xe2x88x92n include silicon tetrachloride; trichlorosilane such as methyltrichlorosilane, ethyltrichlorosilane, phenyltrichlorosilane; dichlorosilane such as dimethylchlorosilane, diethyldichlorosilane, diphenyldichlorosilane, and methylphenyldichlorosilane; monochlorosilane such as trimethylchlorosilane; and a mixture of these silicon compounds can also be used in the present invention, or more preferably silicon tetrachloride can be used.
The amount of the mixture of a titanium compound and a silicon compound used during re-crystallization of the magnesium compound solution is appropriately 0.1xcx9c200 mol per mole of a halogenated magnesium compound, preferably 0.1xcx9c100 mol, or more preferably 0.2xcx9c80 mol. The molar ratio of a titanium compound to a silicon compound in the mixture is appropriately 0.05xcx9c0.95, or more preferably 0.1xcx9c0.8. The shape and the size of the resultant re-crystallized solid components vary a great deal according to the reaction conditions at the time when the magnesium compound solution is reacted with the mixture of a titanium compound and a silicon compound. Consequently, the reaction of a magnesium compound with the mixture of a titanium compound and a silicon compound should be carried out preferably at a sufficiently low temperature to result in formation of solid components. More preferably, the reaction should be carried out by contact-reaction at xe2x88x9270xcx9c70xc2x0 C., or more preferably at xe2x88x9250xcx9c50xc2x0 C. After the contact-reaction, the reaction temperature is slowly raised for sufficient reaction for the duration of 0.5xcx9c5 hours at 50xcx9c150xc2x0 C.
The solid components obtained as above are activated by reacting the same with an aluminum compound. The aluminum compounds used in the present invention for examples include trialkylaluminum having an alkyl group of 1xcx9c6 carbon atoms, such as triethylaluminum and triisobutylaluminum; an aluminum compound having one more halogens, such as ethylaluminum dichloride, diethylaluminum chloride, and ethylaluminum sesquichloride; or the mixtures thereof. Moreover, if necessary, an aluminum compound can be used by diluting it to the solvent. At the time of reacting aluminum, it should be carried out at 0xcx9c100xc2x0 C., or more preferably at 20xcx9c80xc2x0 C.
The solid catalyst is produced by reacting a titanium compound or a mixture of a titanium compound and a vanadium compound with said activated solid components. These titanium compounds used in the present invention are titanium halides, and halogenated alkoxy titanium with an alkoxy functional group of 1xcx9c20 carbons. At times, a mixture of these compounds can also be used. Of these compounds, titanium halide and a halogenated alkoxy titanium compound having an alkoxy functional group of 1xcx9c8 carbons can be appropriately used, or more preferably titanium tetrahalide.
The vanadium compound used in the present invention is a compound with the maximum atomic valence of 4, or the maximum atomic valence of VO of a vanadyl group of 3. It has a general formula of V(OR)4xe2x88x92nXn, or VO(OR)3xe2x88x92mXm. Here, R is an aliphatic or aromatic hydrocarbon group having 1xcx9c14 carbons, or COR1 (R1 is an aliphatic or aromatic hydrocarbon group having 1xcx9c14 carbons). X is Cl, Br or I, and n is an integer of 0xcx9c4, or the ratio thereof. An m is an integer of 0xcx9c3, or the ratio thereof. The examples of these compounds include vanadium tetrachloride, vanadyl trichloride, vanadyl tri-n-propoxide, vanadyl triisopropoxide, vanadyl tri-n-butoxide, vanadyl tetra-n-butoxide and vanadyl tetra-n-propoxide. Among these compounds, one or more compounds can be used.
Further, the catalysts produced according to the present invention can be utilized during polymerization or co-polymerization of ethylene. In particular, the catalyst is used in polymerization of ethylene, and also in co-polymerization of ethylene and xcex1-olefin having three or more carbons, such as propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, or 1-hexene.
The polymerization reaction in the presence of the catalyst of the present invention is carried out by means of using (a) the solid catalyst of the present invention, comprising magnesium, titanium, aluminum, halogen, electron donors, and optionally vanadium, and (b) a catalyst system comprising compounds of organic metals of Groups II and III of the Periodic Table.
The solid titanium catalyst (a) of the present invention can be used after pre-polymerization to ethylene or xcex1-olefin prior to the use in the aforementioned polymerization reaction. The pre-polymerization can be carried out in the presence of a hydrocarbon solvent such as hexane, at a sufficiently low temperature, with ethylene or xcex1-olefin under pressure, in the presence of the above catalyst component and an organic aluminum compound such as triethylaluminum. Pre-polymerization, by maintaining the shape of the catalyst by surrounding the catalyst particles with polymers, is helpful in producing good-quality post-polymerization shape in polymers. The weight ratio of the polymers to the catalysts after pre-polymerization is ordinarily 0.1:1 to 20:1.
The organometallic compound (b) used in the polymerization reaction using the catalyst of the present invention can be represented by a general formula of MRn, wherein, M stands for a metal component of Group II or IIIA in the Periodic Table, such as magnesium, calcium, zinc, boron, aluminum, and gallium; R for an alkyl group with 1xcx9c20 carbons, such as a methyl, ethyl, butyl, hexyl, octyl, or decyl group; and n for the atomic valence of the metal component. As for more preferable organometallic compounds, trialkyl aluminum having an alkyl group of 1xcx9c6 carbons, such as triethylaluminum and triisobutylaluminum, or the mixture thereof can be utilized. On occasions, an organic aluminum compound having one or more halogen, or a hydride group, such as ethylaluminum dichloride, diethylaluminum chloride, ethyl-aluminum sesquichloride, or diisobutylaluminum hydride can also be used.
As for the polymerization reaction, it is possible to carry out either gas phase or bulk polymerization in the absence of an organic solvent, or liquid slurry polymerization in the presence of an organic solvent. These polymerization methods, however, are carried out in the absence of oxygen, water, or other compounds that may act as catalytic poison.
The concentration of the solid titanium compound (a) with respect to the polymerization reaction system, in the case of a liquid phase slurry polymerization, is approximately 0.001xcx9c5 mmol in terms of titanium atom of catalysts per one liter of solvent, or more preferably approximately 0.001xcx9c0.5 mmol. As for the solvent, the following compounds or the mixtures thereof can be used: alkanes or cycloalkanes such as pentane, hexane, heptane, n-octane, isooctane, cyclohexane, methylcyclohexane; alkylaromatic such as toluene, xylene, ethylbenzene, isopropylbenzene, ethyltoluene, n-propylbenzene, diethylbenzene; halogenated aromatics such as chlorobenzene, chloronaphthalene, ortho-dichlorobenzene; and the mixtures thereof.
In the case of gas phase polymerization, the amount of solid titanium catalysts (a) could be approximately 0.001xcx9c5 mmol in terms of titanium atom of catalysts per one liter of a polymerization volume, preferably approximately 0.001xcx9c1.0 mmol, or more preferably approximately 0.01xcx9c0.5 mmol.
The preferable concentration of an organometallic compound (b) is about 1xcx9c2,000 mol, as calculated by aluminum atoms, per mole of titanium atoms in the catalyst (i), or more preferably about 5xcx9c500 mol.
To secure a high reaction rate of polymerization, the polymerization herein is carried out at a sufficiently high temperature, irrespective of the polymerization manufacturing process. Generally, the temperature of 20xcx9c200xc2x0 C. is appropriate, or more preferably approximately 20xcx9c95xc2x0 C. The appropriate pressure of monomers at the time of polymerization is the atmospheric to 100 atm, or more preferably 2xcx9c50 atm.
In the present invention, the molecular weight is expressed as a melting index (ASTM D 1238), which is generally known in the art. The value of the melting index generally becomes greater as the molecular weight decreases.
The products obtained by the method of polymerization using the catalyst of the present invention are solid ethylene polymer or copolymers of ethylene and xcex1-olefin, which have excellent bulk density and fluidity. Since the yield of polymers is sufficiently high, there is no need for the removal of catalyst residues.